17 tooth speedometer gear in a 1940

[Dan Hay]

I bought a 17 tooth model A gear from Brattons. Car is running, but it looks like the mesh is not correct with my 40 worm gear on the driveshaft. It spins intermittently like its skipping teeth.

Do I need to machine down the housing for a better mesh? Or is an 18 tooth as low as I can go with the stock 40 driveshaft gear?

I have 3.54 gears and 750 16 tires. I bought the 17 tooth thinking that would compensate for the bigger tires.

Thanks in advance